test: Add test cases for zero value constructors

Fixed: tint:477
Change-Id: I087c24904ab2f38524ab2c39092fbfb277fdba3b
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/55256
Auto-Submit: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

test/expressions/zero_init/array/struct.wgsl.expected.hlsl

@@ -0,0 +1,18 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+struct S {
+  int i;
+  uint u;
+  float f;
+  bool b;
+};
+struct tint_array_wrapper {
+  S arr[4];
+};
+
+void f() {
+  tint_array_wrapper v = {{{0, 0u, 0.0f, false}, {0, 0u, 0.0f, false}, {0, 0u, 0.0f, false}, {0, 0u, 0.0f, false}}};
+}